title: Methods for calculating forces within quantum Monte Carlo simulations.
abstract: Atomic force calculations within the variational and diffusion quantum Monte Carlo methods are described. The advantages of calculating diffusion quantum Monte Carlo forces with the 'pure' rather than the 'mixed' probability distribution are discussed. An accurate and practical method for calculating forces using the pure distribution is presented and tested for the SiH molecule. The statistics of force estimators are explored and violations of the central limit theorem are found in some cases.
authors.affiliation: Theory of Condensed Matter Group, Cavendish Laboratory, Cambridge CB3 0HE, UK.
authors.forename: A
authors.initials: A
authors.lastname: Badinski
authors.forename: P D
authors.initials: PD
authors.lastname: Haynes
authors.forename: J R
authors.initials: JR
authors.lastname: Trail
authors.forename: R J
authors.initials: RJ
authors.lastname: Needs
mesh_terms: D003198:Computer Simulation; D009010:Monte Carlo Method; D011336:Probability; D011789:Quantum Theory